Archived from groups: microsoft.public.windowsxp.hardware (
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> I don't know about others in this forum, but most of the authors of the
> standard texts on PC repair and A+ training are advocates of POST
> Diagnostic
> cards or debug cards. If one searches the motherboard specific newsgroups
> and the A+ newsgroup in the google groups archive, you'll notice that
> the forum participants who posses an in-depth understanding of PC hardware
> do promote POST diagnostic cards as a useful tool. These would be the
> participants who modify, REPAIR (other than just replacing modules) and
> overclock motherboard hardware on a regular basis. A POST diagnostic
> card is just one of a multitude of diagnostic tools an experienced
> technician would be using.
>
> Another inexpensive tool is a multimeter, most technicians just use it to
> measure DC voltage, but another important test is to measure the AC ripple
> voltage on the DC rails. One also should use an oscilloscope to see how
> "clean" the power supply rails are (look for PSU switching noise and
> spikes).
> Look both at the power supply (PSU) output and at various strategic points
> throughout the system. This electrical low frequency noise and high
> frequency
> noise affects certain motherboard subsystems more than others. Random
> memory
> errors are one example (not as a result of bad memory, but as a result
> of failing capacitors, oxidised contacts etc.). Without an expensive
> oscilloscope to see the high frequency electrical noise one can use a
> POST diagnostic card to see the secondary effects. A "noisy" PSU may have
> perfectly OK DC voltage levels. The type of electronic component used to
> limit and absorb noise and spikes throughout your PC are capacitors. It
> may
> not even be capacitor deterioration in the PSU, the lack of noise
> filtering
> may come from deteriorated capacitors in other subassemblies of your PC. A
> PCI post card or any other diagnostic tool is only as good as the
> understanding
> of person using it. That is, the understanding of the technology and its
> limits.
>
> Note that POST Diagnostic cards are becoming more widely available.
> Vendors
> would not stock or sell POST Diagnostic cards if there is no market or no
> use
> for them. A note of caution to Ryan, the manuals that come with most post
> diagnostic cards and that come with mulimeters just explain the basic
> functions
> of the device and assume that the user has a technical background with
> knowledge
> on how to use the tool. So get yourself some of the better books on the
> subject
> that are published by Sybex, O'Riley, Que and others.
Thanks for your reply. I agree with you in theory. I used to use an
oscilloscope and logic probe to diagnose problems. I used to use a couple of
different POST diagnostic cards as well. They were a lot more than $34.95
back then
That was when the average PC cost over $5,000.00. I could
afford to spend a bit of time to properly diagnose a problem. It was normal
to charge $50.00 for an estimate. Most people won't pay for the time and
effort involved to properly diagnose and repair a PC now. Estimates are free
or the customer is out the door. It is much quicker and cheaper to just
replace parts. With any amount of experience you spend a few minutes talking
to the customer, a few minutes hooking up the PC to a known good monitor,
and give the customer an estimate based on your best guess. About 90% of the
time you are right. The other 10% you lose a bit of money but have a happy
customer. Unfortunately with new PC's running under $500.00 not many people
want to pay more than $200.00 to repair an old one. In Ryan's case I would
have guessed a PSU. It looks like I would have been wrong. I would have
spent an hour or so figuring out what the real problem was, given him
another estimate at no charge and let him take it from there.
Also without training and experience I still think a POST diagnostic card
wouldn't be much use.
Kerry
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